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Discussion Starter · #1 · (Edited)
Have a 07 trailblazer 4.2 been having an issue with the car idling rough and shutting off while I was driving and I had to stop to turn it back on and happened multiple times. When I was on a stop light I found myself having to put it on neutral to keep it running otherwise it would turn off. Took it to a reputable shop they did their diag. and gave me a couple reasons why, gave me codes and the rec. parts to replace which was over 2 grand so I bought the parts and installed them myself ($400) I'm mechanically inclined but no master tech. so even after all that the car still bogs and dies at a stop, low speeds, hills, at cold starts unless I rev up and rpm stays at low 600's.

LIST OF NEW PARTS what the shop rec. replacing
throttle body
MAF sensor
fan clutch
spark plug
EVAP system vent valve solenoid

CODES
p0068, p0101, p0107, p0411, p0449, p0461, p0526, p0856, p2440 half of them went away when the parts where replaced but still have the p0411 which is the secondary air injection system not sure if that should cause the car to act up and at this point I'm lost I don't want to spend no more money on it and need any help!!!
 

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Just wondering... where do you buy gas? Buying low quality fuel, like from a grocery store or discount market, can lead to a rough idle. Try buying 87 octane at a Conoco or Phillips 66.
 

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I was filling up at a gas station that offered free car washes with every fuel purchase of 8 gallons or more, and my 08 4.2L started to idle rough after a few months. It idled rough enough to shake my water bottle in the cup holder. I called my dad for a solution. He has worked in the auto repair industry for 40 years. The first thing he asked me is where I was buying gas. He said run the old gas low and then fill up with a full tank of good gas from Conoco or Phillips 66. My rough idle was fixed after a few miles.
 

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2004 GMC Envoy SLT 4.2
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I was filling up at a gas station that offered free car washes with every fuel purchase of 8 gallons or more, and my 08 4.2L started to idle rough after a few months. It idled rough enough to shake my water bottle in the cup holder. I called my dad for a solution. He has worked in the auto repair industry for 40 years. The first thing he asked me is where I was buying gas. He said run the old gas low and then fill up with a full tank of good gas from Conoco or Phillips 66. My rough idle was fixed after a few miles.
Your Dad knows what he's talking about .
Phillips 66 is my favorite gasoline . Better overall performance , as well as better mileage . ;)
 

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Discussion Starter · #5 ·
Update: Car doesn't shut off no more ended up disconnecting the battery and fuses # 10 Powertrain Control Module B
#28 Powertrain Control Module 1 #56 Air Injection Reactor (AIR) Pump to restart the computer and noticed the intake manifold bolts where loose (hand tight) I was only able to tighten 5 out of the 10 bolts, its a tight squeeze but after that connected everything back up and turned the car on (Note) the car still runs like A SS but now it doesn't die off when cranking , idle at a stop, up hills, I was able to drive for about 20 mins straight without any issue so my guess is the bolts on the intake where loose causing a vacuum leak and causing the car to die or I didn't do the right procedure when I installed the new throttle body in. Any other input would be appreciated!!!

Haven't filled up on gas but ill be on the look out if anything changed.
 

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Just wondering... where do you buy gas? Buying low quality fuel, like from a grocery store or discount market, can lead to a rough idle. Try buying 87 octane at a Conoco or Phillips 66.
I don't have any of those near me. I like Chevron, but none close by either. I was getting ethanol-free gas from Buc-ee's, since I drove it so little during quarantine, and now have been getting Quik Trip gas and putting Sta-bil in it, since I bought the bottle I figured I'd use it up. Planning to get a case of Techron in bottles too. Best one I can think of near me is Exxon, how have you all fared with that? I think I also need injectors and O2 sensors, and probably should have the intake gasket checked. Mine is an 03 4.2 with 316,000 on it. When I first start it, it'll go to high idle but have a big stumble, and that smooths out within a few seconds. It idles smooth until it warms up, at which point it idles rough, in gear or neutral.
 

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2006 Chevrolet Trailblazer LS
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[/QUOTE] When I first start it, it'll go to high idle but have a big stumble, and that smooths out within a few seconds. It idles smooth until it warms up, at which point it idles rough, in gear or neutral.
[/QUOTE]

You have a vacuum leak, my friend.
At start, the computer thinks you are asking for throttle and feeds gasoline to accommodate the extra air.
As the engine warms, the leak gets smaller, and, as the computer takes over in closed loop, it's getting confused - hence the roughness.
 
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